(a) Technical Field
The present invention relates to a system and method for solidifying carbon dioxide into carbonate. More particularly, the present invention relates to a system and method for solidifying carbon dioxide into carbonate in which carbon dioxide is stably converted into and solidified into carbonate (mineral facies) by using steel slag or natural mineral.
(b) Background Art
A solidification technology of carbon dioxide into carbonate is a system and method for disposing of separated/collected carbon dioxide, which has been raised as an alternative technology for geological/deep zone storage. The ultimate object of the technology is to produce a carbon component through conversion of carbon dioxide, and convert the produced carbon component into fuel or a basic compound required for industrial processes.
In other words, the conversion of carbon dioxide into another material such as carbonate provides an environmentally friendly advantage because it removes carbon dioxide from the air which causes global warming. Furthermore, the conversion allows carbon dioxide to be applied as a raw material for industrial basic materials.
As shown in FIG. 1, in conventional solidification of carbon dioxide into carbonate by using steel slag or natural mineral, in order to extract an alkali metal component such as calcium, acetic acid has been used as an extraction solvent. Beneficially, it is possible to maximize the total amount of solidified carbon dioxide since the calcium extraction ratio of acetic acid is much higher than those of other solvents.
However, in solidification of carbon dioxide into carbonate, when a large amount of acetic acid is used as an extraction solvent for extracting an alkali metal component, it is difficult to handle the acetic acid due to strong olfactory acridity. Also, in this case, other components of slag besides calcium may be eluted, and thus many other impurities may be precipitated together with a conversion reaction of carbon dioxide into carbonate. Further, since it is required to add a large amount of sodium hydroxide (NaOH) as a pH adjuster for a carbonate conversion reaction, an additional cost is required. The use of sodium hydroxide excessively produces calcium hydroxide (Ca(OH)2), and thus produces suspended solids, which interferes with the conversion of calcium into calcium carbonate (CaCO3). Thus, the purity of the converted calcium carbonate is low thereby requiring a lot of additional purifying steps. This lowers economical efficiency.
In order to improve the above described problems, in the solidification of carbon dioxide into carbonate, acetic acid has been conventionally substituted by ammonium salt, etc. Then, the use condition of ammonium salt has been optimized so that carbon dioxide can be stably solidified into carbonate.
Ammonium salt is not acrid, unlike acetic acid, and is easy to handle. Especially, in this case, the calcium extraction selectivity is high, and thus during the extraction of calcium from slag, other components except for calcium are hardly eluted. Also, there is an advantage in that since a pH of a solution is increased after the extraction, a carbonate conversion reaction can be efficiently carried out without the addition of sodium hydroxide during the carbonate conversion reaction. Furthermore, there is an advantage in that since there are no other impurity components, it is possible to collect high purity CaCO3. Thus, it is expected to improve the economical efficiency according to a reduction of the consumption amount of sodium hydroxide, and the collection of high purity calcium carbonate.
However, the above described ammonium salt has a low calcium extraction ratio, thereby reducing the ratio of solidification of carbon dioxide. Also, the conventional method for solidifying carbon dioxide into carbonate, as shown in FIG. 2, induces a reaction for extracting an alkali component by using ammonium salt at a very low concentration. Thus, the extraction ratio of calcium from slag is very low.
Also, in the conventional method for solidifying carbon dioxide into carbonate, as shown in FIG. 2, carbon dioxide is injected immediately after calcium extraction without a pH adjusting step, thereby inducing the carbonate conversion reaction. Thus, the final amount of converted carbonate is also not large enough.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.